Rice straw and corn stalks were used as fermentation substrate for the evaluation of cellulases activity secreted by different organisms. The substrates were pretreated with alkaline hydrogen peroxide (AHP) for 6h at 30 and 60<SUP>o</SUP>C. From the fermentation studies, rice straw and corn stalks substrates showed the highest cellulases activity after 96h at 60<SUP>o</SUP>C of pre-treatment.